Research has focused on the cardiovascular effects of adenosine receptor subtype agonists and antagonists in rats and of kappa receptor agonists in squirrel monkeys. Adenosine plays a role in the behavioral effects of caffeine, one of the most widely used drugs in the world. Rats are implanted with telemetry devices for recording blood pressure and heart rate. Various adenosine agonists and antagonists were then administered and blood pressure and heart rate were recorded for 1 hour. We have recently confirmed that the heart rate increasing effects of adenosine A2A agonists are mediated in the central nervous system while other effects of adenosine A2A and A1 agonists are mediated in the periphery. These experiments involved both peripheral and central administration of drug and pretreatment with ganglionic blockers. Currrent studies are focusing on the effects of adenosine agonists and antagonist following chronic caffeine treatment. Kappa agonists have been proposed as treatments for psychostimulant abuse. In squirrel monkeys implanted with arterial catheters kappa agonists produce large increases in heart rate. This is due to the central effects of these drugs as shown in studies with ganglionic blockers. When given in combination with cocaine kappa agonists do not potentiate the effects of cocaine, suggesting that kappa agonists can be used safely in the treatment psychostimulant abuse.